This thesis describes the host-guest chemistry between Cucurbit[7]uril (CB[7]) and CB[8] and a series of guests including bispyridinium cations, phenols and napthalenes. These guests are bound to ruthenium polypyridine complexes or ruthenium based water oxidation catalysts (WOCs). The investigations are based upon utilizing the covalently linked photosensitizer and the electronic effects and chemical processes are investigated.

The binding interactions between cucurbit[8]uril (CB[8]) and a dicationic guest N,N-dimethyl-3,3'-dimethyl-4,4'-bipyridinium (DMV2+) have been investigated by various experimental techniques including NMR, ESI-MS, and UV/Vis and fluorescence spectroscopy. In a three-component system consisting of CB[81, N,N-dimethyl-4,4'-bipyridinium (MV2+) and DMV2+, CB[8] was found to exhibit a higher binding affinity to DMV2+ than to MV2+, When DMV2+ was connected to MV2+ by an alkyl chain, the first equiv. of CB[8] could be selectively positioned on the DMV2+ moiety, and then a second equiv. of CB[8] was positioned on the MV2+ moiety. Spectroelectrochemical studies showed that upon the reduction of this system at -0.6 V vs. AgCl, the CB[8] could move from the DMV2+ moiety to the MV+center dot radical, which formed a dimer inside the CB[8] cavity. Molecular oxygen quenched the dimer, and the CB[8] moved back to the DMV2+ moiety, indicating it molecular movement driven by electrochemistry. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Two mononuclear ruthenium complexes [RuL(pic)(3)] (1) and [RuL(bpy)(pic)] (2) (H2L = 2,6-pyridinedicarboxylic acid, pic=4-picoline, bpy = 2,2'-bipyridine) have been synthesized and fully characterized. Both complexes could promote water oxidation chemically and photochemically. Compared with other known ruthenium-based water oxidation catalysts using [Ce(NH4)(2)(NO3)(6)] (Ce-IV) as the oxidant in solution at pH 1.0, complex 1 is one of the most active catalysts yet reported with an initial rate of 0.23 turnovers(-1). Under acidic conditions, the equatorial 4-picoline in complex 1 dissociates first. In addition, ligand exchange in 1 occurs when the Rum state is reached. Based on the above observations and MS measurements of the intermediates during water oxidation by 1 using Ce-IV as oxidant, [RuL(pic)(2)(H2O)](+) is proposed as the real water oxidation catalyst.

The synthesis of two supramolecular diruthenium complexes, 1 subset of CB[7] and 1 subset of CB[8] (CB[n]=cucurbit[n]uril), which contain the respective host CB[7] and CB[8], were synthesized and isolated. In the case of host CB[8], the desired supramolecular complex was obtained by utilizing dihydroxynapthalene as a template during the synthesis. The (1)H NMR spectra, electrochemistry, and photochemistry of these supramolecular complexes were performed in nonaqueous solution. The results show that both CB[7,8] hosts mainly bind to the linker part in solution in acetonitrile. This binding also lowers the oxidation potential of the ruthenium metal center and hinders the quenching effect by the viologen moiety. It has also been shown that external methylviologen can be included into 1 subset of CB[8]. Analysis with NMR spectroscopy, electrochemistry, and photochemistry clearly shows a viologen radical dimer formation between the bound viologen and free methylviologen, thereby showing that the unique abilities of the CB[8] host can be utilized even in nonaqueous solution.

A stable 1 : 1 : 1 inclusion complex of Ru(bpy)(3)-phenol (1), MV2+ and cucurbit[8]uril (CB[8]) is formed in aqueous solution. In the presence of triethanolamine (TEOA), a light-induced formation of unusual partner radical trimer 1-(MV+center dot)(2)-CB[8] has been observed for the first time.

A stable 1 : 1 inclusion complex of Ru(bpy)(3)-MV2+ with cucurbit[8]uril (CB[8]) is formed in aqueous solution; upon light irradiation, a long lived (tau similar to 2 mu s) charge-separated state Ru3+- MV+.-CB[8] is observed.

Host-guest chemistry and photoinduced electron-transfer processes have been studied in the systems containing Ru(bPy)(3) complex covalently linked to viologen as a guest molecule and cucurbit[n]urils (n = 7, 8) as host molecules in aqueous solution. The Ru(bpy)(3)-viologen complex,[Ru(2,2 '-bipyridine)(2)(4-(4-(1 '-methyl-4,4 '-bipyridinediium-1-yl)butyl)-4 '-methyl-2,2 '-bipyridine)]Cl-4(denoted as RU2+-MV2+, 1) was shown to form stable 1:1 inclusion complexes with cucurbit[7]uril (CB[7]) and cucurbit[8] uril (CB[8]). The binding modes are slightly different with CB[7] and CB[8]. CB[7] preferentially binds to part of the viologen residue in 1 together with the butyl chain, whereas CB[8] preferentially encloses the whole viologen residue. Photoinduced intramolecular electron transfer from the excited-state of the Ru moiety to MV2+ which is inserted into the cavity of the CBs occurred. Long-lived charge-separated states RU3+-MV+center dot, were generated with the lifetimes of 280 ns with CB[7] and 2060 ns with CB[8]. This shows that CBs can slow down the charge recombination within supramolecular systems, and the difference in lifetimes seems to be due to the difference in binding modes. In the presence of a sacrificial electron donor triethanolarnine, light-driven formation of a dimer of MV+center dot inside the CB[8] cavity was observed. This locked molecular dimer can be unlocked by molecular oxygen to give back the original form of the molecular dyad 1 with the MV2+ moiety inserted in the cavity of CB[8]. The processes could be repeated several times and showed nice reversibility.

A 1:1:1 inclusion complex is formed by the binding interactions among beta-CD, CB[ 7] hosts, and Ru(bpy)(3)-terminated viologen naphthalene guest in aqueous solution, in which the positions of both CB[7] and beta-CD are closer to the Ru stopper than in the respective 1:1 inclusion complexes, forming a tightened nut on bolt'' structural mode.

The host-guest chemistry of systems containing a molecular triad Ru(bpy)(3)-MV2+-naphthol complex (denoted as Ru2+-MV2+-Np, 1) and cucurbit[8]uril (CB[8]) is investigated by NMR, EST-MS, UV-vis, and electrochemistry. The Ru2+-MV2+-Np guest and CB [8] host can form a stable 1:1 inclusion complex, in which the naphthalene residue is back-folded and inserted together with the viologen residue into the cavity of CB[8]. The selective binding of Ru2+-MV2+-Np guest with beta-CD and CB[8] host is also investigated. We find that CB[8] binds the Ru2+-MV2+-Np guest stronger than beta-CD. Upon light irradiation, a MV+center dot radical cation stabilized in the cavity of CB[8] accompanied by the naphthalene residue has been observed. This novel system may open a new way for design and synthesis of photoactive molecular devices.